Laminations



United States Patent O 3,511,655 LAMINATIONS Howard C. Haas, Arlington, and Harold 0. Buzzell, Wollaston, Mass., assignors to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Filed Apr. 29, 1965, Ser. No. 451,894 Int. Cl. 603e 5/54 U.S. Cl. 96-29 25 Claims ABSTRACT F THE DISCLOSURE Laminar structures comprising a color photograph bonded to a transparent embossable rigid or semi-rigid vinyl overlay through an intermediate layer of a vinyl lower alkyl ester-vinyl chloride copolymer, the surface of which is hydrolyzed, the image-bearing surface of the color photograph being bonded directly to the hydrolyzed surface of said intermediate layer or being bonded indirectly thereto through a layer consisting essentially of polyvinyl alcohol; and transparent ID cards having this structure.

This invention relates to a novel and improved card that serves to identify its holder.

It is one object of the present invention to provide an identification card, or the like, which comprises a photographic likeness of its holder.

A further object of the present invention is to provide an identification card, or the like, which bears a photographic likeness of its holder in color and which will automatically be defaced by, or will automatically reveal any attempt to change or alter said photographic likeness.

A further object of the present invention is to provide an identification card of the type described above which is durable and which will provide a long and useful service life.

A further object of the present invention is to provide novel laminations comprising photographic likenesses in color which cannot be separated without destroying or defacing said photographic likenesses.

A further object of the present invention is to provide an identification card of the type described above which is suitable for embossing and which is capable of permanently maintaining raised or embossed figures.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties, and the relation of elements which are exemplified in the following detailed disclosure, vand the scope of the application of which -will be indicated in the claims For a full understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

FIG. 1 is a cross-section, greatly magnified, of one stage in the preparation of a lamination made in accordance with this invention;

FIG. 2 is a cross-section, greatly magnified, of a completed lamination made in accordance with this invention;

FIG. 3 is a cross-section, greatly magnified of another embodiment of a lamination made in accordance with this invention;

FIG. 4 is `an illustration of one method of preparing the lamination of this invention;

FIG. 5 represents a plan view of one stage in the preparation of one embodiment of the laminations of this invention;

FIG. 6 represents a section taken along line 6-6 of FIG. 5;

FIG. 7 represents a section of the embodiment shown in FIGS. 5 and 6 when complete; and

FIG. 8 represents a section of the embodiment shown in FIG. 2 when embossed.

Numerous cards have been proposed which are designed to identify their holder to others. Typical examples are the so-called credit cards provided by various commercial enterprises, such as department stores, service stations and the like, automobile drivers licenses, or identification badges, such as those used to identify the personne] of plants or buildings where employees are limited in their right of access to predetermined portions of the plant or building. In such instances, it is of great importance to provide persons with an identification card or badge which is difficult or impossible to counterfeit and which immediately identifies its wearer, preferably by containing a photographic likeness of him. In particular, it is highly desirable to provide a card or badge which comprises a photographic likeness of its holder in color together with any other desired identifying indica, which card or badge is laminated to a transparent rigid or semirigid film by way of a so-called security seal, that is, a seal which cannot be broken or tampered with without immediately clearly rendering obvious the intrusion by destroying or defacing the photographic likeness.

In the case of credit cards, it is also desirable that such cards be embossable with certain information, such as with the holders name, address, or code number. Such embossed cards may be placed in a small imprinter whereby the embossed indicia are applied to a receipt form or the like. Such cards are generally termed self-writing since they eliminate the time that would be required to manually imprint the necessary indicia on the receipt form. It is necessary that such cards have an outer surface comprising a synthetic material capable of providing stable, sharp-edged raised letters or numerals as a result of a suitable embossing procedure, the techniques for which are well known to the art. Synthetic films of the aforementioned nature are conventionally known as rigid vinyls or semi-rigid vinyls, and generally cornprise polyvinyl chloride/vinyl acetate resins which are blends of polyvinyl chloride and polyvinyl acetate or copolymers of vinyl chloride and vinyl acetate, having a relatively high chloride content. In the case of semi-rigid vinyls, a minor amount of a suitable plasticizer, that is a plasticizer which is compatible `with the main polymeric materials and which does not significantly affect their embossability, may also be present.

Where the identification card contains a photographic likeness of its holder, it is desira-ble, in the interest of speed and efliciency, to provide a rapid means of obtaining such a likeness. Of particular advantage in this respect are photographic images of the type which may be produced by color diffusion transfer processes. In such processes a sheet of photosensitive material is exposed to create therein a latent image. The latent image is developed and, concurrent with and under the control of this development, an imagewise distribution of colorproviding material is formed. At least a portion of these color-providing materials is transferred by means of an alkaline aqueous processing solution t0 a superposed image-receiving layer to form a color positive image thereon. As examples of such processes, mention may be made of the processes disclosed and claimed in U.S. Pat. No. 2,983,606 issued May 9, 1961 to Howard G. Rogers, wherein the dye developers (i.e., a dye containing a silver halide developing function and capable of developing exposed silver halide) are the color-providing materials; the processes claimed and disclosed in U.S. Pat. No. 2,647,- 049 issued `luly 28, 1953 to Edwin H. Land, wherein color developes are employed to develop the latent image and color couplers are the color-providing materials; and the processes disclosed in U.S. Pat. No. 2,774,668 issued Dec. 18, 1956 to Howard G. Rogers, wherein complete, preformed dyes which are capable of coupling are used as the color-providing substances.

In color diffusion transfer processes employing dye developers, a latent image in a silver halide photosensitive element is developed in the presence of a dye developer and, as a result of this development, the dye developer in the exposed areas is oxidized and substantially immobilized. At least a portion of the immobilization is believed to be due, at least in part, to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. In unexposed and partially exposed areas of the emulsion, the dye developer is unreacted and diffusible, and thus provides an imagewise distribution of unoxidized dye developer, dissolved in the liquid processing composition, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer or element, said transfer excluding oxidized dye developer. The image-receiving element receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewlise distribution thereof to provide a reversed or positive color image of the developed image.

The image-receiving element used in processes of the aforementioned type generally comprises an opaque or transparent support coated with an image-receiving layer of a dyeable material which is permeable to the alkaline aqueous processing solution. The dyeable material 'prefera-bly comprise polyvinyl alcohol together with a polyvinyl pyridine polymer such as a poly-4-viny1 pyridine polymer. As examples of the image-receiving elements 'just described mention may be made of those materials described in U.S. Pat. No. 3,148,061 issued Sept. 8, 1964 to Howard C. Haas, and in the aforementioned IU.S. Pat. No. 2,983,606.

Diffusion transfer photographic processes of the type described above are particularly adapted for use in a Polaroid Land Camera made by Polaroid Corporation, Cambridge, Mass. 02139, or a smaller camera structure such, for example, as the camera forming the subject matter of US. Pat. No. 2,435,717 issued to Edwin H. Land on Feb. 10, 1948.

Where photographic likenesses of individuals are desired for identification card purposes, the foregoing process' when used in cameras of the aforementioned type renders it possible to obtain such liknesses immediately upon making the photographic exposure, and obviates the necessity of the usual waiting period required for conventional photographic processes wherein a negative must be photoexposed and developed in a separate subsequent operation. However, owing to the nature of the imagereceiving element as described above, it has been found that where it was sought to laminate the final positive color image to any conventional transparent supporting material and particularly to rigid or semi-rigid vinyls by techniques known heretofore, the image layer tends to separate, or be easily separable from, the transparent overlay. This was found to be particularly true when laminatons were sought to be made between the positive color image and transparent supports using heat or pressuresensitive adhesives.

-It has now been found that excellent security seals can be provided between diffusion transfer color photographic images of the aforementioned type and embossable rigid or semi-rigid vinyls comprising polyvinyl chloride/vinyl acetate resins by applying a layer consisting essentially of a copolymer of vinyl chloride and a vinyl lower alkyl ester, such as vinyl acetate, vinyl propionate, and vinyl butyrate, preferably having a vinyl alkyl ester to vinyl chloride molar ratio of from 7:3 to 1:1, to one side of the rigid vinyl; hydrolyzing the surface of the layer so applied; drying the hydrolyzed surface; wetting either the thus-hydrolyzed surface or the surface of a diffusion transfer color photograph; and firmly pressing the surface of the diffusion transfer color photograph onto the hydrolyzed surface. Alternatively, if the image-receiving element which comprises the diffusion transfer color photograph has been freshly stripped from the photosensitive element and is still wet, it may be pressed directly onto the surface of the hydroxylated polymer layer without additional wetting. lf the latter method is employed, i.e., no additional wetting of the image-receiving element prior to lamination, the lamination procedure should take place as soon as possible after the image-receiving element is stripped from the photosensitive element, preferably within 10 seconds thereof. If a longer time is permitted to elapse, while the image-receiving element may still be damp, the moisture remaining on its surface may be insufficient to provide a good security seal.

As was stated previously, the embossible films which are laminated to diffusion transfer color photographs in accordance with this invention comprise high chloride content polyvinyl chloride/ vinyl acetate rigid vinyls, such as Vynex NVH-860, a polyvinyl chloride/vinyl acetate resinous film having an average acetate content of 15% and including minor amounts of appropriate stabilizers, ultraviolet absorbers, lubricants, and the like, commercially available from Nixon-Baldwin Chemicals Inc., Nixon, NJ.; Oriex 7-300-18, a biaxially oriented rigid vinyl similar in composition to Vynex, also available from Nixon-Baldwin Chemicals, Inc.; and VCA-3615 semirigid vinyl, a high chloride content polyvinyl chloride/ vinyl acetate resin similar in composition to the foregoing materials except that it includes a minor amount of an appropriate plasticizer, commercially available from Bakelite C0., a Division of Union Carbide and Carbon Corp., New York, N.Y. The precise ratio of vinyl chloride to vinyl acetate in the rigid or semi-rigid vinyl overlay is not critical in the preparation of laminations characterized by security seals in accordance with this invention, other than that the vinyl comprise a major amount of vinyl chloride and a minor amount of vinyl acetate. However, the vinyl overlay must be both substantially transparent and capable of maintaining embossed figures having permanent sharp edges. Bearing in mind the foregoing limitations, the selection of suitable vinyl yfilms for use in security sealed laminations as described in this disclosure will be apparent to one skilled in the art.

In order to bond rigid or semi-rigid vinyls to diffusion transfer color photographs in a security seal, it is necessary to apply a bonding layer to the vinyl comprising a surface-hydrolyzed vinyl lower alkyl ester-vinyl chloride copolymer having a vinyl chloride content on a molar basis of no more than -about 50% and preferably no less than about 30%. It has been found that if the copolymer contains more vinyl chloride than about 50%, even after surface hydrolysis, the overlay exhibits a tendency to separate from the photograph. Copolymers containing less than about 30% vinyl chloride may also be employed; however, while such materials generally provide satisfactory security seals with semi-rigid, or plasticized, vinyls, they do not always adhere uniformly to the unplasticized rigid vinyls described above. In the preferred embodiment, the vinyl lower alkyl ester is vinyl acetate.

The copolymer may be prepared, for example, by combining the vinyl lower alkyl ester and vinyl chloride in the desired ratio in a suitable pressurized vessel under an inert atmosphere, along with appropriate quantities of a polymerization catalyst, such as ammonium, sodium, or potassium persulfate, benzoyl peroxide, etc., a wetting agent such as sodium lauryl sulfate, and water, and optionally, an emulsion stabilizer such as acetic acid and a redox reaction initiator to decompose the catalyst, such as sodium bisulte. (The last-mentioned material enables the copolymerization reaction to he run at relatively low ternperatures, thereby avoiding undesirable pressure buildup.) The mixture is warmed, stirred, or tumbled, and allowed to react for a suitable length of time, after which the resulting latex is acid-coagulated, filtered, washed and dried.

While the foregoing general procedure was used in the preparation of copolymers for the bonding layer in laminations prepared in accordance with the teachings of this invention, it will be appreciated that suitable copolymers may be prepared by any one of the many techniques known to the art of synthetic resins.

The copolymers so prepared are dissolved in any organic solvent in which they are soluble, preferably a lowboiling ketone such as acetone forVquick-drying properties. The resulting solution is then applied to one side of a rigid or semi-rigid vinyl film as described above and dried.

The surface of the copolymer layer so applied is then hydrolyzed, preferably by the following procedure: The entire film is immersed at a temperature of about 30- 50 C. for a short period of time in a hydrolyzing solution comprising a mixture of a material capable of hydrolyzing the vinyl acetate groups at the surface of the copolymer layer to vinyl alcohol groups, e.g., an alkali metal hydroxide, and a material capable of softening the copolymer layer, such as a water-alcohol blend and preferably, a water-lower alcohol mixture having a water-toalcohol ratio of about 1:1 by volume. It has been found that higher temperatures tend to adversely affect the properties of the vinyl overlay, while lower temperatures require unduly long reaction times.

Where the vinyl lower alkyl ester is vinyl acetate, the preferred reaction time is about seconds at about 40 C. Reaction times of less than about 13 seconds at this temperature, tend to result in insufficient hydrolysis of the acetate groups for a good security seal; longer reaction times effect deeper hydrolysis of the copolymer layer which, while not being detrimental to the security seal, does nothing to enhance it. It will be appreciated that by routine experimentation, the reaction time and temperature required for an effective degree of hydrolysis where other vinyl lower alkyl esters are employed can be readily determined.

After the foregoing treatment the film is washed with Water until its surface is neutral, and dried. I

It is noted that the foregoing procedure effects hydrolysis not only of the surface of the copolymer layer, but also of the outer layer of the rigid or semi-rigid vinyl. For most purposes this makes no difference. However, in those instances where it is specifically desired that only the copolymer surface and not the rigid or semi-rigid vinyl surface be hydrolyzed, other techniques may be employed, such as those described in U.S. Pat. No. 3,078,178 issued Feb. 19, 1963 to Bertil E. Ostberg.

As was stated previously, security sealed laminations comprising diffusion transfer color photographic prints may be prepared by placing the wet surface of the print against the surface hydrolyzed vinyl acetate-vinyl chloride copolymeric layer as described above and pressing the surfaces together. High pressures are not necessary to achieve the security bond, but may aid in the exclusion or expulsion of any air which may be trapped between the layers, and may reduce the time necessary for the bond to setf If the color print is damp immediately prior to lamination, water alone may be used to wet the photographic print surface or the hydrolyzed copolymer surface in order to form a security seal. If the print is thoroughly dry however, while Water alone provides a seal, in the preferred embodiment the water used to wet the surfaces includes dissolved polyvinyl alcohol which provides a doping material. Solutions containing up to 10% polyvinyl alcohol, preferably completely hydrolyzed, have been found to be particularly efficacious in this respect. Higher concentrations of polyvinyl alcohol may be employed but such solutions give no added advantage in the preparation of the lamination and may prove undesirably viscous for mechanical consideration. Moreover, the higher the polyvinyl alcohol concentration in the wetting solution, the longer it takes for the seal to set and dry.

In preparing laminations of the type described above, the wet diffusion transfer photographic image may be simply placed in face-to-face relationship with the hydrolyzed polymeric surface and pressure applied directly. Alternatively, the print to be laminated may be fed, together with the transparent overlay material, between two rolls ordinarily known as V-ing rolls. If the surfaces have not been wet previously, they can be readily wetted during the latter lamination procedure by spreading a droplet of water along one edge of the surface of the print or the hydrolyzed copolymer surface immediately prior to its being fed into the V-ing rolls. The droplet of water then forms at the nip between the surfaces being laminated and passes over the surfaces, thus effectively providing the necessary moisture.

An additional suitable method for simultaneously wetting the surface of the diffusion transfer color print and the laminating it to the transparent overlay is described in U.S. Pat No. 2,798,021 issued July 2, 1957 to Edwin H. Land. In this procedure, the wetting solution is contained in a sealed, rupturable container which when ruptured by a suitable pressure-applying means such as pressureapplying rollers, discharges its contents; means are provided for spreading the contents between the surfaces being laminated.

In certain instances, such as where the vinyl lower alkyl ester-vinyl chloride copolymer layer contains a relatively high percent of vinyl chloride, the hydrolysis techniques described above may not always result in a uniformly hydrolyzed surface. While diffusion transfer color photographs can be satisfactorily bonded to such surfaces in a security seal, it has been found that the uniformity of the seal can be improved by providing a thin layer of polyvinyl alcohol on the hydrolyzed copolymer surface prior to its lamination to the print surface. The simplest procedure for achieving such a layer is coating the hydrolyzed copolymer surface with an aqueous solution of hydrolyzed polyvinyl alcohol, drying the coating, and laminating the polyvinyl alcohol surface to the diffusion transfer color photograph by the same methods described above, in which there was no separate polyvinyl alcohol layer. The concentration of polyvinyl alcohol in the coating solution is not critical, but is preferably less than about 10%, so that the layer can dry in a relatively short time. Alternatively, a thin sheet of poly-vinyl alcohol can be laminated to the hydrolyzed copolymer surface with water, or preferably, water containing up to 10% by weight polyvinyl alcohol, by any of the various methods well known to the laminating art. The outer surface ofthe polyvinyl alcohol sheet is then laminated to the image-bearing surface of the diffusion transfer color photograph by the same techniques described previously.

Security-sealed laminations comprising diffusion transfer color photographs bonded to polyvinyl alcohol surfaces are described and claimed in copending U.S. patent application Ser. No. 451,705 of Robert L. Malster, filed concurrently herewith.

In cases where a separate sheet of polyvinyl alcohol is bonded between the hydrolyzed copolymer-coated vinyl film and the diffusion transfer color photograph as described above, the polyvinyl alcohol sheet may, if desired, comprise a light-polarizer. 'In such instances, a second security feature is added to the final laminated photographic image, in addition to that provided by the security bond. Any attempt to tamper with or otherwise alter the surface of the laminate, e.g., by cutting into the material or heating it, affects the light-polarizing properties of the surface to the extent that the attemped alteration or intrusion can be readily detected with a suitable light-polarizing analyzer. The use of transparent lightpolarizing sheets as a security feature for laminates is described and claimed in the copending U.S. patent application of Robert L. Malster, Ser. No. 451,895, filed concurrently herewith, now U.S. Pat. No. 3,313,052.

Referring now to the drawing, FIG. 1 represents the layers as previously described immediately prior to lamination, comprising a diffusion transfer color photograph 9, a rigid or semi-rigid vinyl overlay 10 on which a layer 11 of vinyl lower alkyl ester-vinyl chloride copolymer has been coated and the surface 12 hydrolyzed. A drop of wetting solution 13 has been placed between the diffusion transfer photograph 9 and surface-hydrolyzed layer 11 which, when spread between the layers, effects their bonding together in a security seal. It will be appreciated that, as described above, if the diffusion transfer color photograph is still wet from photographic processing, wetting solution 13 may be unnecessary.

FIG. 2 represents the structure shown in FIG. 1, in which the wetting liquid has been spread, and the respective layers pressed together to form security bond 14, thus completing the lamination.

FIG. 3 is a cross section, greatly magnified, of another embodiment of the laminations of this invention, wherein a layer of polyvinyl alcohol is interposed between the image-bearing surface of a diffusion transfer color photograph and the copolymer-coated vinyl overlay. As shown, the lamination comprises a rigid or semi-rigid vinyl sheet 10 having bonded thereto a surface-hydrolyzed (12) layer 11 of vinyl lower alkyl ester-vinyl chloride, to the hydrolyzed surface 12 of which is bonded a layer 15 of polyvinyl alcohol. The image-bearing surface of a diffusion transfer color photograph 9 is in turn bonded to the polyvinyl alcohol layer 15.

FIG. 4 is a cross section, greatly magnified, of a laminated diffusion transfer color photograph being prepared by one of the methods described previously. As shown, the sheet materials, comprising the diffusion transfer color photograph 9 and rigid or semi-rigid vinyl sheet 10 with its surface-hydrolyzed (12) layer 11 of vinyl lower alkyl ester-vinyl chloride copolymer, are fed between two V-ing rolls 22 and 16 rotatably mounted and suitably driven in directions indicated by the arrows on the rolls. Rolls 22 and 16 are adjustable with respect to the distances between centers so that a suitable pressure may be brought to bear upon the contacting surface of the sheets. Numeral 13 designates a bead of wetting liquid maintained at the nip between the two sheets of material undergoing lamination adjacent the point of contact. As the bead 13 is forced by the rotation of rolls 22 and 16 over the surfaces of the layers being laminated, it wets the surfaces sufficiently to provide for the formation of security bond 14.

FIGS. through 7 represent a special embodiment of this invention, which may be characterized as an envelope or pouch comprising a diffusion transfer color photograph laminated to one of its inner surfaces in a security bond.

FIG. 5 is a plan view of an envelope or pouch which has been prepared for providing the aforementioned embodiment, prior to lamination. The envelope or pouch comprises Wall 17, which is made up of a transparent rigid or semi-rigid vinyl overlay coated with a surface-hydrolyzed vinyl lower alkyl ester-vinyl chloride copolymer as previously described. Wall 17 is heat, solvent, or adhesive-sealed around a portion of its periphery 1'8 to a non-adhesive backing 19, which is preferably flexible, leaving the remainder of the periphery open for the insertion of the diffusion transfer color photograph.

FIG. 6 is a section taken along lines 6 6 of FIG. 5, and shows the relationship of rigid or semi-rigid vinyl layer with its surface-hydrolyzed (12.) layer 11 of vinyl lower alkyl ester-vinyl chloride copolymer, both of which when taken together comprise the front wall 17 of the envelope, sealed at its periphery 18 to backing 19. It is noted that in the absence of water, the hydrolyzed sur- 8 face 12 will exhibit no tendency to adhere to non-adhesive backing 19.

Envelopes or pouches so prepared provide ready structures for lamination to diffusion transfer color photographs. The photograph is either taken While still fresh and wet from photographic processing, or is mechanically wetted, and is inserted into the pouch or envelope by Way of its open end, in such a way that the image-bearing surface of the photograph is immediately adjacent to the hydrolyzed surface. Thereafter, the entire envelope is subjected to pressure, such as by passing it between V- ing rolls as described above, to provide the security bond. (The use of V-ing rolls to provide the necessary pressure gives the additional advantage that any excess wetting solution can be forced out of the envelope by way of its open end.) Preferably, the envelope is then sealed along its remaining open end.

FIG. 7 is a section similar to that of FIG. 6, showing the relationship of all of the elements when a completed laminate is prepared as just described. The final structure is an envelope or pouch comprising a transparent front wall 17, made up of a vinyl overlay 10 of a rigid or semi-rigid vinyl film having a layer 11 on its inner surface of a surface-hydrolyzed vinyl lower alkyl estervinyl chloride copolymer, to the hydrolyzed surface 12 of which is bonded the image-bearing surface of a diffusion transfer color photograph 9 in a security bond 14. Front wall 17 is sealed about its entire periphery 18 and 20 to non-adhesive backing 19 to provide a sealed, tamperproof lamination.

FIG. 8 represents an embodiment substantially identical to that given in FIG. 2, showing the relationship of the various elements when the lamination has been embossed with raised characters 21.

The following nonlimiting examples further illustrate the present invention:

(A) PREPARATION OF VINYL LOWER ALKYL ESTER-VINYL CHLORIDE COPOLYMER Example I A thick-walled glass bottle was charged with the following:

De-oxygenated water, ml. Dupanol-C (trade name for sodium lauryl sulate), g. 1.25 Ammonium persulfate, g 0.62 Glacial acetic acid, drops 10 Vinyl acetate, distilled, g. 45

Sodium bisulte, g. 0.25 Vinyl chloride, g. 14

The bottle was sealed under an atmosphere of nitrogen and tum-bled at about 45 C. for about 21/2 hours. The resulting latex was coagulated with a small amount of concentrated hydrochloric acid. The coagulated polymer was filtered, Iwashed well with water to remove all traces of the Dupanol-C, dissolved in acetone-methanol, precipitated into Water, and dried. The resulting copolymer had a vinyl acetate to vinyl chloride molar ratio of 7:3.

Example II A copolymer was prepared by the procedure of Example I, except that the bottle was tumbled for a period of about 18 hours; a substantially identical product was recovered.

Example III A copolymer was prepared by the procedure of Example I, except that the glacial acetic acid was omitted from the reaction mixture. A substantially identical product was recovered.

9 (B) PREPARATION OF THE RIGID VINYL OVERLAY Example IV A copolymer prepared by the procedure of Example I having a vinyl acetate to vinyl chloride molar ratio of 7:3 was dissolved in acetone to provide a solution having a concentration of about 1%. The solution was coated onto one side of an extruded high chloride content polyvinyl chloride/vinyl acetate resinous film having an average acetate content of about (commercially available from Nixon-Baldwin Chemicals Inc., Nixon, NJ under the trade name Vynex NVH-860), and the coating thus applied was allowed to dry.

The entire film so treated was immersed for about 15 seconds at about 40 C. in a solution prepared by dissolving 50() g. of sodium hydroxide in a mixture of 500 cc. of water and 500 cc. of methanol. Thereafter, the film was removed from the solution, washed with water until the surface was neutral as determined with pHydrion paper, and dried.

Example V The procedure of Example IV was followed, except the film coated with the copolymer was a plasticized high chloride content vinyl chloride/vinyl acetate semi-rigid vinyl, commercially available from Bakelite Co., a Division of Union Carbide and Carbon Corp., New York, N.Y., designated as VCA-3615 resin.

Example VI The procedure of Example IV was followed except that the film coated with the copolymer was a biaxially oriented polyvinyl chloride-acetate resin having an average acetate content of 15%, commercially available from Nixon-Baldwin Chemicals Inc., under the trade name Oriex 7-300-18.

Example VII The procedure of Example IV was followed except that the copolymer used to coat the rigid vinyl film had a vinyl acetate to vinyl chloride molar ratio of 1:1.

Example VIII A plasticized semi-rigid vinyl film substantially identical to that used in Example V was coated with a 1% solution of polyvinyl acetate in acetone. The coating was allowed to dry, and the film was surface-hydrolyzed by the procedure given in Example IV.

(C) PREPARATION OF SECURITY SEALED LAMINATIONS Example IX A diffusion transfer color photographic image was made using Polaroid Polacolor Land Film, Type 108 and a Polaroid Automatic Model 100 Camera. The image-receptive layer together -with its superposed photosensitive element was pulled from the camera; the elements were maintained in superposed position for 50 seconds, after which they were stripped apart. Immediately after stripping, while the image-receptive surface was still fresh and wet, it was pressed firmly against the surface-hydrolyzed 7:3 vinyl acetate-vinyl chloride copolymer layer on a rigid vinyl film prepared as in Example IV. After a period of about two minutes an attempt was made to separate the photograph from its overlay; it was found that the image adhered firmly to the overlay and could not be pulled away, even with the aid of a razor blade.

Example X A lamination was prepared as in Example IX, except that following stripping from its photosensitive element, the surface of the image carrying layer was allowed to dry completely, and was subsequently wet with a solution of 2% completely hydrolyzed polyvinyl alcohol in water. The resulting lamination exhibited a security bond substantially identical to that of the lamination prepared in Example IX, but there was less tendency for air bubbles to be trapped between the layers.

Example XI A lamination was prepared exactly as in the foregoing example, except that the solution of 2% completely hydrolyzed polyvinyl alcohol in water was swabbed onto the hydrolyzed copolymer surface on the rigid vinyl overlay instead of the image-bearing surface of the photographic print. An identical lamination resulted.

Example XII A diffusion transfer color photograph was prepared as in Example IX and was allowed to dry. The surface of the photograph was wetted with a 2% polyvinyl alcohol solution in water and was pressed firmly against the surface-hydrolyzed 7:3 vinyl acetate-vinyl chloride copolymer layer on a semi-rigid vinyl film substantially identical to that prepared in Example V. The resulting lamination was substantially identical to the one prepared in Example X, except that it exhibited a higher degree of flexibility.

Example XIII A lamination was prepared as in Example XI except that the overlay was a biaxially oriented rigid vinyl film having a layer of surface-hydrolyzed 7:3 vinyl acetatevinyl chloride copolymer, substantially identical to that prepared in Example VI. The resulting lamination Was substantially identical to that prepared in Example X.

Example XIV A lamination was prepared as in Example XI except that the overlay was an extruded rigid vinyl film having a layer of surface-hydrolyzed 1:1 vinyl acetate-vinyl chloride copolymer, substantially identical to that prepared in Example VII. The resulting lamination was substantially identical to that prepared in Example X.

Example XV A 1% solution of vinyl acetate in acetone was coated onto a semi-rigid vinyl film substantially identical to that described in Example V. The coating was allowed to dry, after which it was surface-hydrolyzed following the procedure of Example IV. A diffusion transfer color photograph, prepared as in the foregoing examples, was allowed to dry, and was subsequently wet with a 2% solution of polyvinyl alcohol and pressed firmly onto the hydrolyzed vinyl acetate surface. The resulting lamination was substantially identical to that prepared in Example XI.

Example XVI A one-inch wide strip of a linear dichroic polyvinylenepolyvinyl alcohol light-polarizing sheet having a cellulose acetate butyrate backing, commerci-ally available from Polaroid Corporation, Cambridge, Mass. 02139, and designated as type KN-42, was swabbed with a doping solution consisting of 10% by weight polyvinyl alcohol in water, and was pressed firmly against the surface-hydrolyzed 7:3 vinyl acetate-vinyl chloride layer on a rigid vinyl film prepared as described in Example IV. The image-bearing surface of a diffusion transfer color photograph, prepared as in the foregoing examples and dried, was wetted with the same doping solution, and was then pressed onto the vinyl film in such a way that the polarizer strip was sandwiched between the image-bearing surface and the vinyl film, and covered a portion but not all of the photographic image. The resulting lamination exhibited a security seal similar to those described in the above examples. Where the laminate includes a strip of light-polarizing material, an `additional security feature is added to the final laminated photographic-image as described previously.

l 1 Example XVII A rigid vinyl film was coated with a layer of vinyl acetate-vinyl chloride copolymer and hydrolyzed as in Example IV. An yaqueous solution containing 4% by Weight completely hydrolyzed polyvinyl alcohol was doctored onto the hydrolyzed copolymeric surface and dried. The dry, image-bearing surface of a diffusion transfer color photograph prepared as in the foregoing examples was wet with a solution of 2% completely hydrolyzed polyvinyl alcohol in water, and was then pressed firmly against the polyvinyl alcohol surface on the rigid vinyl. The resulting lamination exhibited a security seal of excellent uniformity, and similar in strength to the seals provided in the foregoing examples.

After initial attempts to separate the laminations of each of the foregoing examples proved unsuccessful, the laminations were subjected to the following test conditions:

(1) Stored at 140 C. for sixteen hours.

(2) Packed in Dry Ice for two hours.

(3) Suspended for ten days over a hot saturated sodium chloride solution.

(4) Refrigerated overnight.

(5) Stored at 100 F. at 80% relative humidity for ten days.

(6) Subjected to dry air at 90 C. for about one hour.

None of the foregoing tests were found to have any affect on the security bond. In test (2) in which the laminates were packed in Dry Ice, the laminates readily shattered; the image could still not be separated from the rest of the laminate, even in a fragmented condition.

The strength of the security seal in laminations prepared in accordance with this invention is totally unexpected, and the theoretical reasons for its formation are not wholly understood. To be sure, diffusion transfer image-receptive elements of the type described above generally comprise at least in part polyvinyl alcohol. However, the bond which forms between the surface of such an element and the surface-hydrolyzed vinyl acetate-vinyl chloride copolymerie layer is considerably stronger than bonds generally formed when simple polyvinyl alcohol surfaces are water-laminated to other polyvinyl alcohol surfaces. It is noted that image-receiving elements of the aforementioned type comprise not only polyvinyl alcohol but also, in addition to the vinyl pyridine polymers mentioned above, they contain dyes, and the residuum of developing reagents, and additionally may contain mordants, hardening agents, and the like, which materials, especially the polyvinyl pyridine, may have some effect on the security bond formation.

It will be appreciated that the term image as used in the foregoing discussion is intended to include not only photographic likenesses of given individuals, but also, especially when applied to identification cards and the like, includes photographically recorded indicia which may form a part of the final picture.

An additional security feature may be provided for the laminations of this invention by printing a so-called security symbol in the photographic image by suitable means at the time of photographic exposure and prior to lamination. For example, where the photographic image on the image-bearing surface comprises a photographic likeness of an individual along with other graphic indicia, the security symbol may comprise a suitable design or pattern which is placed in the optical path during photoexposure in such a way as to form part of the photographic image, overlying a small portion of the edge of the photographic likeness and extending into a portion of the graphic area. Thus, in addition to the protection afforded by the lamination itself, the photographic likeness cannot be cut away from the remainder of the irnage-bearing surface without disrupting the security symbol.

In the preceding portions of the specification, the expression color has been frequently used. This expresl2 sion is intended to include the use of a plurality of colors to obtain black.

Since certain changes may be made in the above process and product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A laminar structure comprising a first layer comprising a transparent, embossable polyvinyl chloride/ vinyl acetate resinous films having a major portion of vinyl chloride and a minor portion of vinyl acetate; a second transparent layer adjacent and bonded to said first layer consisting essentially of a vinyl lower alkyl ester-vinyl chloride copolymer having a chloride to alkyl ester molar ratio of no more than about 1:1, the surface of said layer away from said first layer having been treated with a hydrolyzing solution of alkali metal hydroxide dissolved in a liquid that is a softening `agent for Isaid copolymer to hydrolyze vinyl lower alkyl ester groups of said copolymer to vinyl alcohol groups; and a third layer adjacent to said second layer comprising a diffusion transfer color photograph, the image-bearing surface of which is bonded to said treated surface of said second layer.

2. A la-minar lstructure as defined in claim 1 wherein said vinyl lower alkyl ester is vinyl acetate.

3. A laminar structure as defined in claim 1 wherein said second layer consists essentially of a surface-hydrolyzed vinyl acetate-vinyl chloride copolymer having a vinyl acetate to vinyl chloride molar ratio of 7:3.

4. A laminar structure las defined in claim 1 wherein said image-bearing surface of said diffusion transfer color photograph comprises polyvinyl alcohol and poly-4-vinyl pyridine.

5. A tamper-proof identification card comprising a laminar structure as defined in claim 1.

6. A laminar structure comprising a first layer comprising a transparent, embossable polyvinyl chloride! vinyl acetate resinous fil-m having a major portion of vinyl chloride and a minor portion of vinyl acetate; a second transparent layer adjacent and bonded to said first layer consisting essentially of la vinyl lower alkyl ester-vinyl chloride copolymer having a chloride to alkyl ester molar ratio of no more than about 1:1, the surface of said second layer away from said first layer having been treated with a hydrolyzing solution of alkali metal hydroxide dissolved in a liquid that is a softening agent for said copolymer to hydrolyze vinyl lower alkyl ester groups of said copolymer to vinyl alcohol groups; a third layer adjacent to said second layer and bonded to said treated surface thereof, consisting essentially of polyvinyl alcohol; and a fourth layer adjacent to said second layer comprising a diffusion transfer color photograph, the image-bearing surface of which is bonded to said third layer.

7. A laminar structure as defined in claim 6 wherein said vinyl lower alkyl ester is vinyl acetate.

8. The process for preparing a laminar structure which comprises coating a transparent, embossable polyvinyl chloride/vinyl acetate resinous film having a major portion of vinyl chloride and a minor portion of vinyl acetate with a solution consisting essentially of a vinyl acetate/ vinyl chloride copolymer having a chloride to acetate molar ratio of no more than about 1:1 dissolved in an organic solvent therefor; drying the coating formed thereby; applying to the surface of said coating a hydrolyzing solution comprising an alkali metal hydroxide dissolved in a liquid medium which is a softening agent for said coating at a temperature of about 30 to 50 C. to hydrolyze vinyl acetate groups to vinyl alcohol groups; washing and neutralizing the surface th'us hydrolyzed; and pressing onto said hydrolyzed surface the surface of a diffusion transfer color photograph, at least one of said surfaces being wet when pressed.

9. The process as defined in claim 8 wherein said softening agent for said copolymer coating in ya Waterlower alcohol mixture having a water to alcohol ratio of about lrl-by volume.

10. The process as defined in claim 8 wherein the interface between said diffusion transfer color photograph land said hydrolyzed surface is wetted with water.

11. The process as defined in claim 8 wherein the interface between said diffusion transfer color photograph and said hydrolyzed surface is wetted with an aqueous solution comprising up to 10% by weight polyvinyl alcohol.

12. In the process for preparing a laminar structure which comprises developing a latent image contained in an exposed silver halide emulsion layer with an aqueous alkaline processing solution in the presence of at least one dye developer to thereby provide in said emulsion layer a predetermined distribution of unoxidized dye developer, transferring at least in part said distribution of unoxidized dye developer by imbibition 4from said emulsion layer to an image-receiving layer in superposed relationship with said emulsion layer to impart to said image-receiving layer a reversed, positive dye image of the developed image; stripping said image-receiving layer from said emulsion layer, providing thereby a diffusion transfer color photographic print; and applying an overlay to the surface of said print; the improvement which comprises pressing the image-bearing surface of said diffusion transfer color photographic print, while still wet from photographic processing, onto a transparent overlay comprising a transparent, embossable polyvinyl chloride/vinyl acetate resinous film having bonded thereto a layer consisting essentially of a vinyl acetate/vinyl chloride copolymer having a chloride to acetate molar ratio of no more than about 1:1, the surface of said copolymer having been treated with an alkali metal hydroxide hydrolyzing solution to hydrolyze vinyl acetate groups to vinyl alcohol groups, said print being bonded to said overlay by said hydrolyzed surface.

13. An envelope structure comprising a first transparent wall, which first wall comprises a first outer layer comprising a transparent, embosable polyvinyl chloride/ vinyl acetate resinous film and a second inner layer `bonded to said first layer consisting essentially of a vinyl lower alkyl ester-vinyl chloride copolymer having a chloride to alkyl ester molar ration of no more than about 1:1, the surface of said second layer away from said first layer having been treated with a hydrolyzing solution of alkali metal hydroxide dissolved in a liquid that is a softening agent for said copolymer to hydrolyze vinyl lower alkyl ester groups of said copolymer to vinyl alcohol groups; and a second wall, which second wall comprises a backing for said first wall, and which backing is sealed along a portion of its periphery to said first wall.

14. The structure as defined in claim 13 wherein said vinyl lower ester is vinyl acetate.

15. A tamper-proof, embossable laminar structure comprising a first wall, which first wall comprises a first outer layer comprising a transparent, embossable polyvinyl chloride/ vinyl acetate resinous film, a second inner layer bonded to said first layer consisting essentially of a vinyl lower alkyl ester-vinyl chloride copolymer having a chloride to alkyl ester molar ratio of no more than about 1:1, the surface of said second layer away from said first layer having been treated with a hydrolyzing solution of alkali metal hydroxide dissolved in a liquid that is a softening agent for said copolymer to hydrolyze vinyl lower alkyl ester groups of said copolymer to vinyl alcohol groups; and a third layer comprising a diffusion transfer color photographic print, the image-bearing surface of which is bonded to said treated surface of said second layer; and a second wall, which wall comprises a backing for said first wall, and which backing is sealed about its periphery to said first wall.

16. A structure as defined in claim 15 wherein said vinyl lower alkyl ester is vinyl acetate.

17. The process for preparing a tamper-proof, embossable laminar structure which comprises the steps of:

(a) coating a surface of a transparent, embossable polyvinyl chloride/vinyl acetate resinous film having a major portion of vinyl chloride and a minor portion of vinyl acetate with a solution consisting essentially of a vinyl acetate-vinyl chloride copolymer having a chloride to acetate molar ratio of no more than about 1:1 dissolved in an organic solvent therefor;

(b) drying the coating formed thereby;

(c) treating the dried surface of said coating with a hydrolyzing solution comprising an alkali metal hydroxide dissolved in a liquid medium which is a softening agent for said coating at a temperature of about 30 to 50 C. to hydrolyze vinyl acetate groups to vinyl alcohol groups;

(d) washing the surface thus hydrolyzed with water until it is neutral;

(e) juxtaposing the film so prepared on a planar backing having an identical geometric shape in such a way that said hydrolyzed surface is adjacent to said backing;

(f sealing said film along a portion of its periphery to said backing;

(g) wetting the image-bearing surface of a diffusion transfer color photographic print with an aqueous solution;

(h) inserting said diffusion transfer color photograph into the opening between said film and said backing in such a way that the wet image-bearing surface of said diffusion transfer color photographic print is directly adjacent to said hydrolyzed surface;

(i) pressing the thus-formed laminar structure, thereby expressing wetting solution and forming a security seal between said diffusion transfer color photographic print and said film; and

(j) sealing the remaining portion of the periphery 0f the structure.

18. A transparent, embossable film structure comprising a first layer comprising a transparent, embossable polyvinyl chloride/vinyl acetate resinous film having a major portion of vinyl chloride and a minor portion of vinyl acetate, and a second layer adjacent and bonded to said first layer consisting essentially of a vinyl lower alkyl ester-vinyl chloride copolymer having an alkyl ester to about 1:1, the surface of said second layer away from said first layer having been treated with a hydrolyzing solution of alkali metal hydroxide dissolved in a liquid that is a softening agent for said copolymer to hydrolyze vinyl lower alkyl ester groups of said copolymer to vinyl alcohol groups.

19. The structure as defined in claim 18 wherein said vinyl lower alkyl ester is vinyl acetate.

20. A process for preparing a transparent, embossable film structure which comprises coating one surface of a transparent, embossable polyvinyl chloride/vinyl acetate resinous film having a major portion of vinyl chloride and a minor portion of vinyl acetate, with a solution consisting essentially of a vinyl acetate-vinyl chloride copolymer having an acetate to chloride molar ratio of from about 7:3 to about 1:1 dissolved in an organic solvent therefor; drying the coating formed thereby; treating the surface of said coating with a hydrolyzing solution comprising an alkali metal hydroxide dissolved in a liquid medium which is a softening agent for said coating for at least about 15 seconds at a temperature of between about 30 C. and 50 C. to hydrolyze vinyl acetate groups to vinyl alcohol groups; and washing the surface thus hydrolyzed with water until it is neutral.

21. The process as defined in claim 20 wherein said alkali metal hydroxide is sodium hydroxide.

22. The process as defined in claim 20 wherein said liquid medium consists essentially of a water-lower alcohol mixture having a Water to alcohol ratio of about 1:1

ing a first layer comprising a transparent,` embossablepolyvinyl chloride/vinyl acetate resinous iilrn having a major portion of vinyl chloride and a minor portion of vinyl acetate; a second layer adjacent and bonded to said first layer consisting essentially of a Vinyl lower alkyl ester-vinyl chloride copolymer having an alkyl ester to chloride molar ratio of from about 7:3 to 1:1, the surface of said second layer away from said first layer having been treated with a hydrolyzing solution of alkali metal hydroxide dissolved in a liquid that is a softening agent for said copolymer to hydrolyze vinyl lower alkyl ester groups of said copolymer to vinyl alcohol groups; and a third layer consisting essentially of polyvinyl alcohol bonded to the hydrolyzed surface of said second layer.

24. The structure as defined in claim 23 wherein said vinyl lower alkyl ester is vinyl acetate.

.25. The process as defined in claim 8 wherein said image-bearing surface of said difusion transfer color photograph comprises polyvinyl alcohol and poly-4-vinyl pyridine.

16` References Cited UNITED STATES PATENTS 2,458,639 1/ 1949 Quasies 260-43 2,983,606 5/ 1961 Rogers 96--3 2,647,049 7/ 195 3 Ford 96-29 2,774,669 12/ 1956 Rogers 96--3 3,148,061 9/1964 Hass 96-3 2,397,272 3/ 1946 Land 88-65 2,882,63 1 4/1959 Boone 40-130 OTHER REFERENCES Smith, Vinyl Resins, pp. 137-39, 1961.

NORMAN G. TORCHIN, Primary Examiner J. E. CALLAGHAN, Assistant Examiner U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3 511 655 Dated May l2 1970 Invent0r(s) Howard C. Haas and Harold O. Buzzell It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l2, line lO (application claim l [Amendment D] page 2) "films" should be --film-.

Column l3 line 56 (application claim 14, line 2) after "vinyl lower" insert -alkyl.

Column 14, line 36 (application claim 17 [Amendment D] page 8) after "expressing" insert -excess.

Signed and sealed this 20th day of April 1971.

(SEAL) Attest:

EDWARD M.F'LETCHER,J1-%. WILLIAM E. SCHUYLER, JH. Attestng Officer Commissioner of Patents 

